Magneto-encephalography (MEG) is a non-invasive neuroimaging technique for mapping brain activity. Recording probes are placed on the surface of the skull to record activity occurring on the surface of the brain. Using triangulation techniques, brain activity detected by the probes can be mapped in three dimensions.
Electromagnetic fields are generated in the brain by the flow of ionic currents through neurons during synaptic transmission. Whilst the magnitude of the electromagnetic field associated with individual neurons is typically negligible, the effects of many neurons (e.g. 50,000 to 100,000) excited together in a specific area of the brain generate a measureable electromagnetic field. Since neuro-magnetic signals generated by the brain are weak (typically 10 fT to 1 pT at the point of detection), highly sensitive magnetometers are required in order to detect and locate the neuro-magnetic signals precisely.
SQUID (superconducting quantum interference device) sensors are state of the art sensors currently used for Magneto-encephalography applications. Whilst SQUID sensors are highly sensitive, a considerable drawback to their application is that SQUID sensors require cryogenic cooling. Moreover, since SQUID sensors operate at cryogenic temperatures (typically below 10K), they cannot be placed directly on the skull, without some form of temperature insulation. As a result, of this separation, the neuro-magnetic signals are not as clear as they could be if the sensors were able to be positioned directly on the skull. Moreover, cryogenic cooling is typically performed with liquid helium which is both an expensive and a finite resource, which is projected to be exhausted in 20 years. Accordingly, there is a strong need for a highly sensitive sensor that can be operated at room temperatures.
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